Means for forming circular tunneling.



I J. w. MORGAN.

MEANS FOR FORMING CIRCULAR TUNNELING. APPELICAIION FILED FEB. 19. 1911;

JOHN W. MORGAN, OF MILWAUKEE, WISCONSIN.

MEANS FDR FORMING CIRCULAR TUNNELING.

Specification of Letters Patent.

Patented Feb. 5, 1918..

Application filed February 19, 1917. Serial No. 149,566.

To all whom it may concern:

Be it known that 1, JOHN MORGAN, a citizen of the'United States, andresident of Milwaukee, inthe county of Milwaukee and State of llisconsin, have invented certain new and useful Improvements in'Means forForming Circular Tunneling; and I do hereby declare that the followingis a full, clear, and exact description thereof.

My invention relates to new and useful improvements in means for formingcircular tunnels for conveying sewage or other fluid and including aconcrete body molded in place within the tunnel.

The usual method heretofore employed of projecting tunnels of thisnature, particularly in soft ground has been to dig a tunnel of squarecross section, lined with suitable bracing means to resist pressure ofthe earth, and then to mold concrete in the tunnel to form a cylindricalinterior surface. In view of the clearance necessary between the bracing means and the minimum desired thicle ness of concrete, and in viewof the square shape of the tunnel, which forms the outer mold of theconcrete body, a great wastage of concrete is involved, this wastageamount ing to substantially sixty per cent. of the amount of concretenecessarilyemployed in the formation of the sewer.

Although tunnel bracing means circular in cross section have heretoforebeen provided, such means has been adapted either for use only in hardground, or has necessitated a complicated digging machine for use insoft ground.

It is therefore primarily the object of my invention to provide a meanscircular in cross section for simultaneously forming and bracing atunnel projected through either hard or soft ground, which involves aminimum amount of material, which presents a circular cross sectionwhereby the minimum necessary amount of concrete may be employed inmolding the shell of the sewer, and which may be assembled in the tunnelcoincident with the digging thereof without the provision of initialmeans for holding back the earth.

With the above and other objects and advantages in view, the inventionresides more particularly in the novel combination, formation andarrangement of parts hereinafter described and pointed outin theappended claims.

In the drawings:

Figure l is a vertical sectional view through a sewer shaft and bracingembodying my invention.

Fig. 2 is an end view of a section of'the bracing and molding.

Referring now more particularly to the accompanying drawings, thetunneling operation is first started by the provision of a verticalshaft from which the horizontal tunnel is projected, and in carrying outmy invention I first dig a section of the horizontal tunnel in which toplace an initial section A of my bracing means. This section of bracingmeans comprises at its rear end a circular band 5 formed ofsemi-circular sections of transversely flat metal and of a diametersubstantially equal to the desired diameter of the tunnel. Disposedwithin this band and ofslightly lesser diameter is a second hand 6formed of. semi-circular angle iron strips, the ends of which aresecured together by bolts passed therethrough and through connectingplates '7. The diameters of these bands are such as to provide anannular space therebetween, and in this space are disposed the rear endsof a series of lagging boards or stares 8, the forward ends of theselagging boards being sharpened at 9 to permit said boards to be driveninto theground. Disposed within this series of lagging boards andbearing against said boards. at their inner ends to support them is thetransversely flat circular band 5 of a second section B of bracing,including the inner rear end band 6 and lagging boards 8.

In the operation of digging the tunnel, the first bracing section A isassembled within a previously dug tunnel section. The circular band 5 ofthe next bracing section is then inserted in the first bracing sectionand disposed at the inner end thereof. The inner band 6 is theninserted, in a disassembled position. It is then expanded to its properdiameter, with its ends secured by the connecting plates 7'. Wedges,such as shown at 10 in connection with the bands 5" and 6" of a thirdbracing section are then driven between the rings to hold them inconcentric relation and the lagging boards of the second section arethen driven between the rings, it being understood that this drivingaction of the lagging boards is effected coincident with the removal ofearth from the tunnel portions bounded thereby.

'Thus the tunnelingmay proceed for any desired length, and in view ofthe relatively small amount of material embodied in the bracing,together with the Circular shape thereof, an exceedingly great economyof material and of concrete is procured, it being appreciated that anysuitable and preferably Conventional core member, the outer periphery ofwhich is indicated at 11, would be provided within the sections, inpouring the concrete.

In gravel or water laden eartlrwherein the earth has a tendency to run,the usual breast boarding is set up at thehead of the tunnel and theupper curved bracing portions are set in place and held by the usualneedle beam structure while the bracing section is completed, thisneedle beam structure comprising a longitudinalbeam which is disposed atthe top of the tunnel to engage and support the semi-circular strips,the needle beam structure being supported by a standard set up in thetunnel and being thus readily removable upon completion of the section.Thus my improved method 3f projecting circular tunnels may be uti-.lized in ground of any nature. I am aware disposed in place forms anouter cylindrical mold wall for the body of concrete, the essentialfeature of my invention resides not in the provision of a, cylindricalmold wall,

but in the provision of a. means for tunneling involving the assembly ofa cylindrical bracing means simultaneously with the tunneling operation.

What is claimed is:

1. The method of projecting circular tunnels which consists inpositioning concentric spaced rings transversely in the tunnel, indriving lagging boards between said rings, in removing the dirt in thespace inelosed by the lagging boards, in positioning a second pair ofcircular rings within thev forward ends of series of lagging boards, andin driving a second series of lagging boards between said second pair ofrings and removing the dirt from the space bounded by said second set oflagging boards.

2. A tunnel comprising a circular series of lagging boards having theirends disposed in overlapped relation, and circular bracing ringsdisposed within each end of each series of lagging boards, certain ofsaid rings being disposed between the over lapped ends of the boards.

3. A tunnel comprising a series of lagging boards having their endsdisposed in overlapped relation, bracing rings engaging one end of eachseries of lagging boards at the inner wall thereof, retaining andguiding rings engaging the ends of said lagging boards engaged by saidbracing rings at the outer wall thereof, said retaining rings be ingdisposed between the overlapped ends of the boards, substantially asdescribed.

In testimony that I claim the foregoing I have hereunto set my hand atMilwaukee, in the county of Milwaukee and State of Visconsin, in thepresence of two witnesses. JOHN V. MORGAN. lVitnesses FRANK S.R-A'rcmrrn,

M. E. DOWNEY.

Copies of this patent maybe obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. 0.

